Praseodymium chloride

In addition to the coupled-signal method just described, phosphorylated carbon signals can be detected by use of praseodymium chloride, which displaces a- and /8-carbon resonances of a,/8-D-mannose 6-phosphate and a-D-mannosyl phosphate downfield, with little effect on other resonances. Europium chloride has analogous properties, except that the displacements are upfield. With certain polysaccharides, such as the O-phosphonomannan of Hansenula capsulata (29), the sig-... 

Praseodymium oxide (Pr O ) was obtained from Aldrich and used without further purification. Praseodymium chloride (PrCl3) was prepared from praseodymium chloride hexahydrate (Aldrich 99.9%) by heating at ca. 150 C in air. 

The adsorption of carbon dioxide or oxygen on praseodymium samples was measured by a constant-volume method using a calibrated Pirani vacuum gauge. Praseodymium oxide was heated in oxygen (4 kPa) at 775°C for 1 h, then evacuated at 750°C for 0.5 h just before the measurement. The sample of praseodymium oxychloride was prepared from praseodymium chloride by heating under oxygen flow... 

Praseodymium chloride pretreated in a helium flow at 750°C for 1 h produced a low conversion of methane and selectivity to C2+ compounds after 0.5 h on-stream both in the absence and presence of TCM (Figure 2 and Table I). When TCM was present, the conversion and selectivity increased to 17.1 and 46.4% after 1.8 h onstream, respectively, and then the values remained almost constant. In the absence of TCM, the conversion and selectivity also increased to 16.0 and 54.5%, respectively, after 1.8 h on-stream while in the latter case the values decreased gradually to 11.7 and 37.2% over 6 h on-stream. Although no TCM was added to the feedstream, methyl chloride was formed in the reaction. After 0.5 h on-stream, the selectivity to methyl chloride was 2.6% but decreased to 0.1% over 6 h onstream. The XRD pattern of the catalyst after the reaction with TCM present in the... 

Stable catalytic activity was observed with praseodymium chloride pretreated under an oxygen stream at 750°C for 15 h (Figure 4). The longer pretreatment produced high selectivity to C2+ compounds, that is, 58.8% in the presence of TCM and 58.5% in the absence of TCM after 0.5 h on-stream while methane conversions were 19.7 and 18.6%, respectively. Without TCM the conversion and the selectivity decreased gradually to 17.0 and 54.0% after 6 h on-stream, respectively. The catalytic activity was partially restored by addition of TCM to the reaction stream for 1 h. The conversion was 17.3% and the selectivity was 55.0% after 0.5 h on-stream following the period of the TCM feeding. The BET surface areas of the catalysts measured after the reactions in the presence and absence of TCM were both 1.5 m g The XRD patterns of the catalysts used for the reactions were identical with that of praseodymium oxychloride. A small amount of methyl chloride was detected when praseodymium chloride was used as a precursor of the catalyst both in the presence and in the absence of TCM. 

Adsorption of carbon dioxide or oxygen on the praseodymium samples was carried out in the pressure range of 1-40 Pa to evaluate the number of chemisorption sites on the samples. Praseodymium oxide irreversibly adsorbed 9.5 x 10" mol g of carbon dioxide. The amount of oxygen irreversibly adsorbed on the sample was 15.2 x 10" mol g Carbon dioxide or oxygen was not adsorbed on the samples containing chlorine, i.e., praseodymium chloride and praseodymium oxychloride prepared from the chloride by heating under oxygen flow at 750°C for 1 h. 

Figure 2 Conversion and C2+ selectivity for oxidative coupling of methane in the presence and absence of TCM over praseodymium chloride preheated in helium.

In the case of the praseodymium oxychloride produced from praseodymium oxide by the reaction in the presence of TCM (white-green portion), an O Is peak at 529.3 eV with a shoulder at 531 eV was observed. The peak shifted to 528.9 eV after xenon ion-sputtering for 0.5 min. The peak of Pr 3d was similar to that for praseodymium chloride, that is, the main peak was observed at 932.9 eV with a shoulder at 928 eV which was more clearly defined than that in the spectrum for praseodymium chloride. The peak shifted to 932.5 eV after the sputtering and the shoulder at 928 eV intensified as seen in the spectra for praseodymium chloride. The peak of Cl 2p was present at 198.8 eV and the position of the peak did not change after the sputtering. 

There were two peaks at 528.9 and 531.1 eV in the spectrum for O Is of the praseodymium oxychloride taken from the inlet portion of the reactor after the reaction in the absence of TCM (the sample originated from praseodymium chloride heated at 750°C for 1 h). The peak at 531.1 eV disappeared after xenon-ion sputtering while the main peak was present at 529.1 eV. The spectra for Pr 3d before and after xenon-ion sputtering were similar to those for praseodymium oxychloride which originated from praseodymium oxide. Although the Cl 2p spectra for the... 

Praseodymium oxychloride produced from praseodymium chloride with a pretreatment in oxygen followed by methane conversion in the presence of feedstream TCM (as shown in Figure 3) displayed an O Is peak at 529.0 eV but no shoulder. The peak position did not change after xenon-ion sputtering. The spectra for Pr 3d were similar to those for other praseodymium oxychloride samples. The binding energy of Cl 2p was 198.9 eV while the peak had a shoulder at 200 eV. The shoulder disappeared after the sputtering. 

No adsorption of carbon dioxide or oxygen was observed on either praseodymium chloride or oxychloride. This finding is consistent with the XPS results. The main peaks at 529 eV in the spectra for praseodymium oxychloride samples are also attributed to the lattice oxygen of the oxychloride while the peaks at 531 eV are assignable to O Is for praseodymium oxide, suggesting that the surfaces of the oxychloride samples are partially oxidized to praseodymium oxide. The 3d binding energy of 933 eV for praseodymium in the chloride and oxychloride implies that the valence of praseodymium is 3+, while the shoulder at 928 eV could be attributed to metallic praseodymium (77). 

Varsanyi (7/2), in an interesting paper, reported the observation of some very unusual infrared fluorescence in PrCl3 Nd3+ crystals. He observed that when praseodymium chloride containing a few tenths of a per cent neodymium is illuminated with a small-filament lamp, very intense and... 

An interesting example of the salting out by nonelectrolytes in water was given by Grigorovich and Samoilov (69). They studied the solubility of praseodymium chloride and sulfate in water in the presence of various nonelectrolytes (methyl alcohol, ethyl alcohol, and diethyl ether.) Their results show that the decrease in solubility of praseodymium chloride is only of the order of a few percent but that this decrease is probably highly significant because praseodymium chloride is more soluble in pure methyl and ethyl alcohol than in pure water. (The... 

The vesicles were prepared as previously described (1). All divalent cations were added to the solution prior to sonication. In one experiment 5mM praseodymium chloride was added to the vesicle suspension after... 

The only complexes of lanthanum or cerium to be described are [La(terpy)3][C104]3 175) and Ce(terpy)Cl3 H20 411). The lanthanum compound is a 1 3 electrolyte in MeCN or MeN02, and is almost certainly a nine-coordinate mononuclear species the structure of the cerium compound is not known with any certainty. A number of workers have reported hydrated 1 1 complexes of terpy with praseodymium chloride 376,411,438), and the complex PrCl3(terpy)-8H20 has been structurally characterized 376). The metal is in nine-coordinate monocapped square-antiprismatic [Pr(terpy)Cl(H20)5] cations (Fig. 24). Complexes with a 1 1 stoichiometry have also been described for neodymium 33, 409, 411, 413, 417), samarium 33, 411, 412), europium 33, 316, 411, 414, 417), gadolinium 33, 411), terbium 316, 410, 414), dysprosium 33, 410, 412), holmium 33, 410), erbium 33, 410, 417), thulium 410, 412), and ytterbium 410). The 1 2 stoichiometry has only been observed with the later lanthanides, europium 33, 411, 414), gadolinium, dysprosium, and erbium 33). 

In most of these systems there is clear evidence for the formation of the reduced ion For example, in NdX2 salts this is on the basis of magnetic studies (3J), and with the praseodymium chloride and bromide phases, from qualitative resistivity measurements and their structural relationships to the neodymium chlorides according to x-ray data. Cryo-scopic data for all the systems listed are also consistent with the formation of a as opposed to solute in dilute solution in MX3 (3, 7). 

Cr2HKO oCio, Chromate, (ji-hydrido-bis-[pentacarbonyl-, potassium, 23 27 CsCIsSc, Cesium scandium chloride, 22 23 CsCl7Pr2, Cesium praseodymium chloride, 22 2... 

Pd2Cl2P4C5,H44, Palladium(I), (x-carbonyl-dichlorobis[methylenebis(diphenyl-phosphine)]di-, 21 49 PrCL, Praseodymium chloride, 22 39 PrFi8Ns06Pi2C72H72, Praseodymium(III), hexakis(diphenylphosphinic amide)-, tris(hexafluorophosphate), 23 180 PrN30,3C8H,6, Praseodymium(III), trini-trato( 1,4,7,10-tetraoxacy clododecane)-, 23 151... 

ClfJ i SjCtHu, Niobium(III), di- x-chloro-tct-rachloro- x-(dimcthyl sulfide)-bis-(dimethyl su fide)di-, 21 16 Cl7CsPr2, Cesium praseodymium chloride,... 

CsCl7Pr2, Cesium praseodymium chloride, 22 2 Cs2Clo 3oN4PtC4, Platinatc, tctracyano-, cesium chloride (1 2 0.30), 21 142 Cs2C1,Lu, Cesium lutetium chloride, 22 6 CsjCl iTm, Cesium lithium thulium chloride, 20 10... 

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